The predicted climate condition resulting from a large scale nuclear war. The explosions would launch enormous amounts of particles of dust and soot into the stratosphere, and the ashes could remain there for weeks to years. The sunlight would be blocked, and the combination of darkness, cold, radiation, and destruction of world infrastructure by the nuclear bombs could easily wipe out much plant life, including necessary crops. This would in turn cause starvation up through the food chain, eventually causing a massive exctinction of all life on the planet.

North Korea, America, Pakistan, India, Russia, and China all launched nuclear bombs to counter the enemy's nuclear bombs, causing a nuclear winter in just two days. Eight weeks later, every human was dead.

The ecological and environmentaldevastation that would follow a nuclear war. It is often disputed whether the result would be very hot or very cold. Most scientists agree, nuclear winter would - at first - be very very hot. Then oh sooooo cold. Brrrr.

Example 1: Our hotel room was so hot last night, it was a damn nuclear winter.

Example 2: Our hotel room was so cold last night, it was a damn nuclear winter.

A bullshit scenario concocted during the Cold War to scare the US into giving in to the Soviets.
It goes like this: the fires produced by the nuclear bombing of targets would inject large amounts of smoke into the atmosphere. The smoke would coalesce into a layer that would block sunlight from reaching Earth's surface. A massive drop in temperatures would result. Here's where the scare tactics kick in: the lack of sunlight would deprive plants of vital energy, causing an extinction event.
This sob story was busted in a 1986 paper called "Nuclear Winter Reappraised." However, the paper was ignored, and fear of nuclear winter continues to subsist.

The people who came up with "nuclear winter" were not objective scientists but partisan agitators. Their goal was to see the U.S. back down from the Cold War. The most prominent scientist, Carl Sagan, was an enthusiastic proponent of nuclear disarmenent.